I. Field of the Invention
This invention relates generally to signalling apparatus, and more particularly to a device attachable to an electric appliance for providing a visual signal to a farmer or rancher that the appliance is not properly operating, the signal being visible from great distances.
II. Discussion of the Prior Art
While the present invention finds many applications on a farm or ranch where various electrically operated devices are used and a fault condition must be signaled so that effective and prompt attention can be applied, it will be described as applied to use with electric fence systems. It is to be understood, however, that the device can find wide usage on a farm or ranch to signal failure of confinement barns ventilation systems, motor-driven pumps for irrigation and/or stock watering systems, etc. Electric fences have long been used to confine animals, such as horses, cattle, sheep and hogs. The principles of operation of such fences are well known. High voltage impulses of a predetermined duty cycle are applied from a fence generator to one or more fence wires which are strung between posts or insulators so as to define the perimeter of the field or pasture in which the animals are to be confined. When an animal brushes against the energized wire, a path to ground is established through the animal and an uncomfortable shock is delivered. The animals learn quickly that if they are to avoid being shocked, they may not touch the fence and, accordingly, they tend not to break through the fence to roam in undesired areas.
Conditions can arise that may cause the electric fence to malfunction. For example, a branch may fall from a tree and come to rest against the fence so as to create a short circuit to ground through the branch. Similarly, wet grass can grow up to a height where it, too, significantly decreases the amplitude of the voltage pulses traversing the fence line so that they may no longer deter the grazing animals from knocking the fence down or breaking through it. Malfunction can also occur if an animal such a deer breaks the electric fence wire. It is important when such conditions arise that the farmer or rancher be apprised of the malfunction so that corrective action can be taken before the animals can stray.
Geoffrey Begg U.S. Pat. No. 4,523,187 describes a monitoring system for an electric fence which includes a voltmeter for sensing the voltage of the pulses on the fence and an ammeter for sensing the current level flowing through the fence wire. If the voltage drops significantly or the current level increases, a short circuit condition is detected. Likewise, if the current flow read by the ammeter drops to zero, an open circuit condition is indicated. The monitoring system of the Begg patent is physically disposed proximate the pulse generator used to energize the fence and is designed to give, by means of a meter reading, an indication of the voltage level at the far end of the fence. When the signal levels fall outside of a predetermined threshold setting, an audible alarm 18 is operated. The device of the Begg patent is deficient in that it does not provide an indication of the location along the fence line where the fault has occurred which, of course, makes troubleshooting the fence line more difficult.
The McCutchan et al. U.S. Pat. No. 4,297,633 describes an electric fence monitoring system in which a plurality of remotely located responders are operatively coupled to the electric fence for providing responses back to a receiver located at the site of the fence generator. If there is a break in the fence wire, the responder cannot, within a predetermined time interval, deliver its response signal upon receipt of a fence energizing pulse and, accordingly, an alarm is indicated at the receiver site.
Another fairly simple electric fence monitoring system is described in the Pope et al. U.S. Pat. No. 4,220,949. It includes a monitor circuit, including a relay, at the end of the fence opposite from the fence-charging circuit. In the event of a break, the relay switches its contacts to couple an alarm into circuit with a power supply. The device of the Pope et al. patent is incapable of indicating to the farmer or rancher the approximate location where the fault in the fence has occurred. Again, this compounds the effort in making appropriate repairs.